From a perspective as a History teacher and parent this is an excellent resource to learn about Nelson Mandela and the fight for civil rights around the world from about 8-11 years old. It is also ideal for use in Key Stage 3 as an example of primary sources, and also the interpretation of said sources as our main storyteller was only 18 months old at the time of her father's incarceration (this isn't to disrepute the information given, only a point of discussion to explore with children, how might Zindzi Mandela have 'filled in' those gaps in her knowledge- would this have been from a primary or secondary source?) and the wonderful role and value of these eyewitness first-hand accounts to give life and vibrancy to facts, dates and figures. What gives this an extra warmth outside of the usual books about inspirational people is the familial slant, Zindzi Mandela is teaching her own grandchildren about their heritage, not just from the account of what famously happened to their great grandfather (very little is actually discussed about why he was imprisoned, what he did whilst in prison and how that became inspirational too etc) but much is made of the conditions and experience of people of colour in Apartheid era South Africa and the impact of their great-grandfathers incarceration on the family especially the children.
The only warning I give is that the sections on the black experience during apartheid era are hardgoing for younger children especially with the accompanying images, so I would take these pages with a note of caution to assess the sensitivity of your child when reading this. With a great awareness that those with privilege require shaking up and being uncomfortable to encourage a greater understanding and empathy for those without privilege, personally, I don't think this is quite a best fit for the youngest children without a lot of explanation and contextualisation as it may frighten them that these things might happen to them too, because the understanding of chronological awareness (differentiation of past and present) is something that happens in the brain after the reorganisation that occurs from age of 7. This isn't a criticism, nor an attempt to deny or downplay anything, just a statement of the context and tone within the book and the possible reactions and questions that children might raise from my experience of interaction with upsetting history.